Fluorescence kinetics of chloroplasts as indicators of disorders in the photosynthetic system I. Comparative studies with greening leaves of Vitis and Hordeum

Kinetics of both delayed fluorescence (luminescence) and prompt fluorescence of chlorophyll are used to characterize photosynthetic activity in leaf tissues. In a first attempt the greening process in etiolated Vitis cuttings and Hordeum seedlings was studied. Data sampling and processing, including averaging of the kinetics, was carried out by means of a microcomputer. Parallel to the light-induced development of photosynthetic activity the kinetic changes (i. e. luminescence decrease, fluorescence rise and decrease) became more prominent and transitory secondary peaks appeared. For both plants the succession of the kinetic characteristics was the same; it only differed in the time of appearance. The kinetics are discussed according to interpretations given in literature. The method is proposed as a tool to quickly characterize certain damages of the photosynthetic system in different plants

Auswirkungen der Landwirtschaft auf physikalische und chemische Funktionen Europäischer Torfböden

Torfböden bieten zahlreiche Funktionen: sie bilden den weltweit größten terrestrischen Kohlenstoffspeicher, stellen wichtige Nährstofffilter dar und erhöhen hydrologische Pufferkapazitäten. Torfböden sind in Mittel- und Nordeuropa zum überwiegenden Teil landwirtschaftlich genutzt. Kultivierung führt zu extremen Mineralisierungsraten der organischen Substanz und hohen THG-Emissionen. Die Anfälligigkeit für Bodensackung, Boden- und Wasserqualitätsverschlechterung und folglich Ernteausfall steigt. Das Ziel dieser Studie ist es, Auswirkungen des Agrarmanagements auf Funktionen von Torfböden in Europa zu analysieren. In Deutschland, den Niederlanden, Dänemark, Estland, Finnland und Schweden wurden standardisierte Bodenkartierungen, bodenphysikalische und -chemische Analysen, Grundwassermonitoring und Betriebsdatenerhebungen durchgeführt. Die Ergebnisse belegen einen starken Einfluss der bisherigen Bewirtschaftung auf die Funktionen von Torfböden in Europa. Torfböden unter intensiver Ackernutzung bieten im Vergleich zu extensiver und intensiver Grünlandnutzung die niedrigste Tragfähigkeit in den oberen 10 cm, welche eine erfolgreiche landwirtschaftliche Praxis auf Torfböden stark einschränkt. Der Unterschied lässt sich allein durch Wurzelstabilisierung erklären, da die Bodenverdichtung in den oberen 25cm unter Ackernutzung am höchsten ist. Hieraus folgt eine starke Verringerung der nutzbaren Feldkapazität und der gesättigten hydraulischen Leitfähigkeit, wodurch sich hydrologische Probleme wie Staunässe und Trockenstress, die häufig auf kultivierten Torfböden vorkommen, weiter intensivieren. Bodenkohlenstoffvorräte sinken deutlich mit steigender Nutzungsintensität und sind im Vergleich auf extensivem Grünland am höchsten. Dies wird bestätigt durch den Zersetzungsgrad, der hier am niedrigsten ist. Die Ergebnisse deuten auf eine starke Auswirkung des Managements auf Bodenkohlenstoffverluste und Torfkonservierung auf europäischer Ebene hin

Measurement of the W-pair Production Cross-section and W Branching Ratios at s\sqrt{s}=205 and 207 GeV

The cross-section for the process e+e-->W+W- was measured with the data sample collected by DELPHI at centre-of-mass energies up to 209 GeV and corresponding to a total integrated luminosity of about 209 pb^-1. The branching ratios of the W decay were also measured; from them the value of |Vcs| was extracted. The results are compared with the most recent calculations in the frame of the Standard Model

Mobile HTS SQUID System for Eddy Current Testing of Aircraft

In Non-Destructive Evaluation (NDE), eddy current techniques are commonly used for the detection of hidden material defects in metallic structures. Conventionally, one works with an excitation coil generating a field at a distinct frequency. The eddy currents are deviated by materials flaws and the resulting distorted field is sensed by a secondary coil. Because of the law of induction, this technique has its limitations in the low frequency range. This leads to a decrease of the Probability of flaw Detection (POD) in larger depths

Measurement and Interpretation of Fermion-Pair Production at LEP energies above the Z Resonance

This paper presents DELPHI measurements and interpretations of cross-sections, forward-backward asymmetries, and angular distributions, for the e+e- -> ffbar process for centre-of-mass energies above the Z resonance, from sqrt(s) ~ 130 - 207 GeV at the LEP collider. The measurements are consistent with the predictions of the Standard Model and are used to study a variety of models including the S-Matrix ansatz for e+e- -> ffbar scattering and several models which include physics beyond the Standard Model: the exchange of Z' bosons, contact interactions between fermions, the exchange of gravitons in large extra dimensions and the exchange of sneutrino in R-parity violating supersymmetry.Comment: 79 pages, 16 figures, Accepted by Eur. Phys. J.

Determination of the b quark mass at the M_Z scale with the DELPHI detector at LEP

An experimental study of the normalized three-jet rate of b quark events with respect to light quarks events (light= \ell \equiv u,d,s) has been performed using the CAMBRIDGE and DURHAM jet algorithms. The data used were collected by the DELPHI experiment at LEP on the Z peak from 1994 to 2000. The results are found to agree with theoretical predictions treating mass corrections at next-to-leading order. Measurements of the b quark mass have also been performed for both the b pole mass: M_b and the b running mass: m_b(M_Z). Data are found to be better described when using the running mass. The measurement yields: m_b(M_Z) = 2.85 +/- 0.18 (stat) +/- 0.13 (exp) +/- 0.19 (had) +/- 0.12 (theo) GeV/c^2 for the CAMBRIDGE algorithm. This result is the most precise measurement of the b mass derived from a high energy process. When compared to other b mass determinations by experiments at lower energy scales, this value agrees with the prediction of Quantum Chromodynamics for the energy evolution of the running mass. The mass measurement is equivalent to a test of the flavour independence of the strong coupling constant with an accuracy of 7 permil.Comment: 24 pages, 10 figures, Accepted by Eur. Phys. J.

A Determination of the Centre-of-Mass Energy at LEP2 using Radiative 2-fermion Events

Using e+e- -> mu+mu-(gamma) and e+e- -> qqbar(gamma) events radiative to the Z pole, DELPHI has determined the centre-of-mass energy, sqrt{s}, using energy and momentum constraint methods. The results are expressed as deviations from the nominal LEP centre-of-mass energy, measured using other techniques. The results are found to be compatible with the LEP Energy Working Group estimates for a combination of the 1997 to 2000 data sets.Comment: 20 pages, 6 figures, Accepted by Eur. Phys. J.

Study of Tau-pair Production in Photon-Photon Collisions at LEP and Limits on the Anomalous Electromagnetic Moments of the Tau Lepton

Tau-pair production in the process e+e- -> e+e-tau+tau- was studied using data collected by the DELPHI experiment at LEP2 during the years 1997 - 2000. The corresponding integrated luminosity is 650 pb^{-1}. The values of the cross-section obtained are found to be in agreement with QED predictions. Limits on the anomalous magnetic and electric dipole moments of the tau lepton are deduced.Comment: 20 pages, 9 figures, Accepted by Eur. Phys. J.

A Measurement of the Tau Hadronic Branching Ratios

The exclusive and semi-exclusive branching ratios of the tau lepton hadronic decay modes (h- v_t, h- pi0 v_t, h- pi0 pi0 v_t, h- \geq 2pi0 v_t, h- \geq 3pi0 v_t, 2h- h+ v_t, 2h- h+ pi0 v_t, 2h- h+ \geq 2pi0 v_t, 3h- 2h+ v_t and 3h- 2h+ \geq 1pi0 v_t) were measured with data from the DELPHI detector at LEP.Comment: 53 pages, 18 figures, Accepted by Eur. Phys. J.